In electrostatic copying, an electrostatic latent image is formed on an element and is developed into a visible and transferrable image by the application of toner powder thereover. The developed toned image is commonly then transferred from the element to a receiver sheet using an electrostatic bias applied between the element and the receiver sheet. Thereafter, the toned image on the receiver sheet is heat fused and bonded thereto.
A number of useful charge-control agents and transfer agents are known, but the search continues for materials that provide improvements in toner thermal stability and fusibility without detracting from transfer efficiency or triboelectric properties.
Certain fluorinated compounds are known to the prior art for use in toner compositions such as tetrafluoroborates in U.S. Pat. No. 4,454,214; "organofluoro compounds" in U.S. Pat. No. 4,468,446; "fluorinated surfactants" of U.S. Pat. Nos. 4,198,477; and 4,139,483; "perfluoro organic acid derivatives" of U.S. Pat. No. 3,948,654; and the like. Certain onium compounds have previously been taught for use in toner compositions (see, for example, U.S. Pat. Nos. 4,812,381; 4,684,596; 3,893,935; 4,537,848; and 4,496,643).
So far as now known, however, nothing in the prior art has taught or suggested the use of fluorinated onium compounds in methods for increasing toner electrostatic transfer efficiency from an element to a receiver sheet.